1. Technical Field
This invention relates to loudspeakers, and more particularly, to a loudspeaker plastic cone body.
2. Related Art
A loudspeaker cone is a well-known part of every mid and low frequency loudspeaker. In addition, it is well known that a desirable loudspeaker cone body is one with sufficient amount of stiffness and minimized weight. This is known as stiffness to weight ratio. A specific modulus, Ys=Ye(Young's Modulus)/specific gravity, is defined as a figure of merit to compare and rank alternate materials and compositions.
Many of today's loudspeaker cone bodies are made of paper. Unfortunately, paper cone bodies may exhibit moisture problems. In addition, manufacturing tolerances of paper cone bodies are undesirably large.
Some cone bodies are made with polypropylene and may be made by injection molding. Although moisture and repeatability may be less of an issue with unfilled polypropylene, such cone bodies still exhibit a relatively low stiffness to weight ratio due to a relatively low modulus of un-reinforced polypropylene. Incorporating a filler reinforcement such as talc into the polypropylene improves its stiffness (flexural modulus) but reduces plastic flow during injection molding. Thus injection molding of larger cone bodies with thin wall sections is difficult. Further, such fillers increase material specific gravity so that the weight of a cone design increases as well. Therefore, to obtain sufficient stiffness characteristics, the weight of cone bodies may become undesirably high for optimal acoustic performance.